superclusters of galaxiesmischak/teaching/universe/fs2016/presentation_14.pdf• 1958: abell...
TRANSCRIPT
Contents
• What are superclusters of galaxies? • Historic background • Structure and geometry • The Laniakea Supercluster
What are superclusters of galaxies?
• Groups of galaxies – contain up to 50 galaxies – 1 to 2 Mpc (3.3 x 106 to 6.6 x 106 lyrs)
What are superclusters of galaxies?
• Clusters of galaxies – contain up to a thousand galaxies – 2 to 10 Mpc (6.6 x 106 to 33 x 107 lyrs)
What are superclusters of galaxies?
• Superclusters of galaxies – contain more than 105 galaxies – 33 Mpc or more (100 x 106 lyrs)
• Estimated 10 million superclusters in the observable universe
• Traditionally defined by distribution
Structure and Geometry: The Traditional Approach
• Not bound by gravity
• Large voids of space in superclusters
• Subdivided into galaxy clouds
Old definition for superclusters not very precise!
The Laniakea Supercluster
• Laniakea: Hawaiian for immeasurable heaven
• 153 Mpc in diameter (500 x 106 lyrs)
The Laniakea Supercluster
• New definition of superclusters: – All galaxies are flowing towards a
gravitational attractor.
• The Great Attractor – Every galaxy in Laniakea drifting towards it at
a speed of several hundred kilometers per second (peculiar velocity)